Filtering devices that are percutaneously placed in blood vessels have been available for many years. A need for filtering devices can arise, for example, in trauma patients, orthopedic surgery patients, neurosurgery patients, or in patients having medical conditions requiring bed rest or non-movement. During such medical conditions, the need for filtering devices arises where there is a likelihood of thrombosis in the peripheral vasculature of patients wherein clot material, stenosis material or other particles break away from the vessel wall, risking downstream blockage of the vessel or other damage. For example, depending on the size, such break-away material could pose a serious risk of pulmonary embolism, i.e. wherein blood clots migrate from the peripheral vasculature through the heart and into the lungs. A filtering device can be deployed in the vasculature of a patient when, for example, anticoagulant therapy is contraindicated or has failed. In more recent years, filters have been used or considered in preoperative patients and in patients predisposed to thrombosis which places the patient at risk for embolism.
The benefits of a vascular filter have been well established. However, in many cases filters have not been considered removable from a patient due to the likelihood of endotheliosis of the filter or fibrous reaction matter adherent to the endothelium during treatment. Following deployment of a filter in a patient, proliferating intimal cells can begin to accumulate around the filter struts which contact the wall of the vessel. After a length of time, such ingrowth may prevent removal of the filter, or may risk significant trauma during removal through a layer of endothelium, requiring the filter to remain in the patient. Thus, filtering devices may remain implanted in the patient for life, even though the condition or medical problem that required the device has passed, because of difficulty or risk in removal. Where removal has been considered, some filters have been provided with a hook for gripping and pulling (e.g. by intravascular forceps or other catheter-borne device) in order to remove it. Such hooks can be difficult to find or latch onto in vivo, and may be covered by cellular growth.
Accordingly, devices and methods dedicated to easier and more effective removal of intravascular filters are needed.